Singapore’s popular east coast beaches remained closed on the first day of a month—long school holiday on Friday, as an oil spill from a damaged tanker also hit parts of the northern shores, authorities said.

On Tuesday, an estimated 2,500 tons of crude oil leaked from the Malaysian—registered tanker MT Bunga Kelana 3 into the sea after the vessel collided with a bulk carrier about 13 kilometres south—west of Singapore.

“About 90 per cent of the affected areas of East Coast Park have been cleaned up,” the National Environment Agency said in a statement, adding that the beaches stretching about 7 kilometres were still closed.

On Friday, the oil spill also hit a 700—metre—long beach on Singapore’s north—east coast, it said, prompting authorities to close the area for water sports.

In addition, some oil patches had been sighted near a nature reserve on the northern island of Pulau Ubin, the agency said.

As a precautionary measure, authorities had earlier put a boom along the island’s shores to protect its biodiversity.

Depending on the wind and the sea, any remaining oil patches might still be brought to Singapore’s coast in the next few days, the agency said.

The Maritime and Port Authority said “no significant patches of oil” had been spotted in the waterways off the east coast or in Singapore’s anchorages.

The damaged tanker had been safely moved to a Malaysian anchorage in Johor province, it said.

The vessel, operated by Malaysian company AET, collided with the bulk carrier MV Waily, registered under the flag of St Vincent and the Grenadines, in one of the world’s busiest shipping routes along the Singapore and Malacca straits.